There are few Brazilian studies on prevalence of mental disorders in suicide attempters. The available studies have mainly used secondary data and screening instruments. The principal objective of this study was to estimate the prevalence of mental disorders in 96 suicide attempters seen in an emergency ward in Rio de Janeiro, Brasil (2006-2007) using the Composite International Development Interview. Most were female, young, and illiterate, and the main method was ingestion of psychoactive drugs. Other factors included history of prior attempts and use of alcohol at the time of attempt. The most frequent mental disorders were: depression (38.9%), use of psychoactive substances (21.9%), posttraumatic stress disorder (20.8%), alcohol abuse (17.7%), and schizophrenia (15.6%). Total prevalence of mental disorders was 71.9%. These findings are largely consistent with studies conducted in other developing countries. Besides access to treatment for mental disorders, public policies with an emphasis on the control of suicide methods and social responses for the reduction of suicidal behavior are needed.